Teaching System Administration with Linux

System administration is a vital
necessity of any computer system. However, most universities don't
teach system administration. So where do people learn how to become
system administrators? Basically, they have to learn it on their
own. The next logical question is: what enables someone to learn
how to do system administration? Our answer: system administration
requires a fundamental understanding of how operating systems (OS)
and networks operate. However, unlike a traditional computer
science operating system or networking course, which teaches
low-level (i.e., programming) details, system administration
requires only an understanding of theory and fundamentals. For
example, you don't have to know about page table layouts to
understand how to install and configure swap space.

Here at Grand Valley State University we've developed a
course that teaches operating system and networking fundamentals
while using system administration as an underlying theme. Our
students are information systems majors who would otherwise never
learn about the principles of OSes and networking. In the course we
cover OS topics such as users, groups, file sharing and processes,
along with networking topics such as application layer protocols,
the transport layer and network device configuration.

The course has two components: traditional lecture where we
teach the concepts and principles of OS and networking, and a lab
where the students are able to apply the concepts learned in
lecture to a “real-world” environment. Other papers of ours (see
Resources) discuss the organization of the course. Our purpose here
is to show how Linux is used to support the lab for the
course.

The EOS Linux Lab

The Exploratory Operating System (EOS) lab consists of 24
Pentium IIIs with 128MB RAM, 10GB HD, a floppy and a Zip disk. Each
machine is running Red Hat 6.2. The lab is a production
environment—it serves as the primary account of most CS and IS
majors as well as several faculty. Thus, the lab is not a pure
research lab. Real people use the lab every day. Because our lab
isn't a dedicated research lab, giving root access to a group of 24
students every semester is out of the question. However, the
students require superuser access to perform even the most basic
system administration duties.

Our solution is to take advantage of the 100MB Zip disk on
each machine to provide a dedicated Linux distribution to each
student. Each student creates a boot floppy and a root file system
on a Zip disk. With this setup, the student can insert both disks
and reboot the machine. The student then has a working Linux
distribution all to themselves, and one they are able to administer
for themselves. In this environment the student can perform the
experiments for the lab that day. When they're finished, they
simply shut down the machine, remove their floppy and Zip disks and
reboot. The system then comes up in the normal EOS lab
configuration.

Floppy Boot Disk Creation

Currently, the floppy boot disk kernel is based on the 2.2.13
kernel, and no special kernel source modification is required.
However, we do configure the kernel (using
make xconfig) in two special ways.
First, we configure the kernel with SCSI emulation
(CONFIG_CHR_DEV_SG and CONFIG_SCSI are set to true). We have IDE
Zip disks and run them under SCSI emulation because it seems that
the IDE driver doesn't handle large files well.

Our second configuration modification is to disable all
access to the hard disk. Remember, we normally run a standard,
multiuser Red Hat system in the lab. If we didn't disable access to
the hard disk, the student could boot their Zip disk, mount the
hard disk and have carte-blanche to make changes (like changing
root's password). We disable hard disk access by setting two
configuration variables to false, CONFIG_BLK_DEV_IDE and
CONFIG_BLK_DEV_HD_IDE.

Other kernel configuration options enable the network device,
enable SysV init, etc. Once the kernel is configured, we simply
compile it. See the Kernel how-to for more information.

Installing the kernel on a floppy disk is done by creating a
new ext2 file system on the floppy (using mke2fs) and copying the
kernel to the root of the floppy. The floppy disk also requires a
boot block (cp /boot/boot.b /mnt/floppy) and a
special LILO configuration shown below: